Radio repeaters are used to enhance coverage and capacity of radio networks. In the downlink a radio repeater receives the signal transmitted from the base station, amplifies it and transmits the amplified signal such that it may be received by the terminal. In the uplink the repeater works in the opposite way.
A radio relay is a unit capable of decoding incoming signals and encoding the decoded signals into new signals to be forwarded. The complexity allows typically for reduction of noise and if necessary change of applied modulation and coding. Typically, a relay introduces a certain time delay. A repeater is a simpler piece of equipment that essentially without time delay amplifies and forwards a radio signal. The modulation and coding format of the transmitted signal is always equal to the originally received signal. An operating relay is typically known by the system and registered to a specific base station, while the existence of a repeater may be totally transparent also during operation.
In the published U.S. patent application US 2006/0166618, an adaptive relay management is disclosed. Usage requirements in a cell are evaluated and the number and/or type of relays used in the cell are varied in order to meet the usage demands. Instructions about the required configuration are broadcasted to the relays for configuring/registering thereof. In this way, the system ensures that enough resources are available to meet the user requirements.
Since the output power of a radio repeater may be relatively low in comparison to the output power of a base station, it may often be needed to deploy multiple radio repeaters in a cell in order to provide high data rate coverage in a large part of the cell area. A specific user terminal, however, may typically only hear one or a few of the radio repeaters. Accordingly, when the base station transmits (unicast) data destined to a particular user terminal it would be enough that the radio repeaters that enhance the reception quality of this particular user terminal are active. Other radio repeaters do not improve the reception quality. On the contrary, these repeaters cause unnecessary interference and their transmission consumes power without making any good. Such unnecessary power consumption is in particular a drawback for battery powered repeaters, which may be the case e.g. for some movable repeaters.
A general problem in prior art use of repeaters is thus that the use of repeaters typically causes unnecessary radio signaling, thereby increasing interference and power consumption.